Hundreds of migrants may have entered or been allowed to stay in Britain when they should have been refused, according to a report published today.

John Vine, the chief inspector of borders and immigration, also found that the backlog of entrepreneur visas awaiting a decision rose by 1,520 per cent to more than 9,000 between February and December 2012.

He said the Home Office had underestimated the number of students who would use this route to try to remain in Britain when it stopped graduates staying on to work after ending their studies. Staff suspected that many of those applying